1. Field of the Invention
The present invention relates to an apparatus and method for manufacturing a semiconductor device. More particularly, the present apparatus is used to carry a wafer during the semiconductor manufacturing process and includes a sensor for sensing a mis-loaded wafer.
2. Description of the Related Art
Semiconductor devices are manufactured through a multi-step process. A wafer, held in a cassette, is transferred through each step of the process until the semiconductor device is complete. During the multi-step process, one or more of the wafers may be removed or added from the cassette and subjected to a subsequent process step, either individually or in a batch mode. For example, during a wet etching step or a cleaning step, the cassette containing the wafers is placed in a processing bath containing a reactive solution for batch processing. In this case, the cassette is composed of a material, e.g., quartz or TEFLON (a non-stick, heat resistant coating), which is stable in the presence of the reactive solution.
However, as the diameter of the wafer increases beyond the standard eight inch wafer currently used, the size of a cassette necessary to hold and transfer the wafer would be too large to employ with standard manufacturing equipment. One solution would be to enlarge the manufacturing equipment to accommodate the larger sized cassette; however, the cost involved in increasing the size of the manufacturing equipment is prohibitive.
A more cost-effective method employs a guide with a plurality of slots, where the wafers are unloaded onto the guide from the cassette and subsequently moved to a second guide in a processing bath by a robot arm. The guide is illustrated in FIG. 1.
In FIG. 1, the plurality of wafers 20 are separated from the cassette and loaded onto the guide 10 having a plurality of slots 30. A wafer 20A is shown improperly loaded in slot 30 of guide 10. In the device illustrated in FIG. 1, it is impossible to determine whether there are any mis-loaded wafers. An undetected mis-loaded wafer 20A can be dropped and broken during transfer to a second guide, for example, a guide in a processing bath having the same pitch. Also, a wafer 20, during transfer to the second guide may be mis-loaded onto the second guide and dropped in the processing bath, resulting in wafers of different batches mixing in the same processing bath.